Dick has been the standard shortened form (nickname) for Richard for hundreds of years.
The fact that the same word became used as slang for penis is *probably* coincidental.
So the real question to ask is: "why did "dick" come to mean penis?"

Just as the word "pussy" originally meant a cat - again, I suspect the slang came along later.

Lots of other examples: the word "tit" until quite recently only meant "a small bird". It might even have become slang for breast due to the analogy between a breast and a small bird.

And far more recently, the word "gay" only meant "very happy". Again, the slang meaning came along later.

im so sick of crappy fml's about names. like seriously ur not stuck with it forever. if it bothers u that bad save some money and go get it legally changed. dont come on fml complaining which created the worse fml of the day :-)

People name their children a lot worse than this. Be happy you're not named after a sexual organ or sexually transmitted disease simply because your parents were ignorant and thought the word sounded interesting. I've seen children named Vagina and Chlamydia because their teenage ghetto mothers thought they were "pretty words".

I used to nanny for a 2nd grade teacher and one year she had a girl named Shithead ( the -th- like THink and rhymes with reed). She had sooo many parents call and question her when she sent home the Valentines day list LOL!!